This application relates generally to optical routing and more specifically to microelectromechanical systems for routing optical signals.
The Internet and data communications are causing an explosion in the global demand for bandwidth. Fiber optic telecommunications systems are currently deploying a relatively new technology called dense wavelength division multiplexing (DWDM) to expand the capacity of new and existing optical fiber systems to help satisfy this demand. In DWDM, multiple wavelengths of light simultaneously transport information through a single optical fiber. Each wavelength operates as an individual channel carrying a stream of data. The carrying capacity of a fiber is multiplied by the number of DWDM channels used. Today DWDM systems employing up to 80 channels are available from multiple manufacturers, with more promised in the future.
In all telecommunication networks, there is the need to connect individual channels (or circuits) to individual destination points, such as an end customer or to another network. Systems that perform these functions are called cross-connects. Additionally, there is the need to add or drop particular channels at an intermediate point. Systems that perform these functions are called add-drop multiplexers (ADMs). All of these networking functions are currently performed by electronicsxe2x80x94typically an electronic SONET/SDH system. However SONET/SDH systems are designed to process only a single optical channel. Multi-wavelength systems would require multiple SONET/SDH systems operating in parallel to process the many optical channels. This makes it difficult and expensive to scale DWDM networks using SONET/SDH technology.
The alternative is an all-optical network. Optical networks designed to operate at the wavelength level are commonly called xe2x80x9cwavelength routing networksxe2x80x9d or xe2x80x9coptical transport networksxe2x80x9d (OTN). In a wavelength routing network, the individual wavelengths in a DWDM fiber must be manageable. New types of photonic network elements operating at the wavelength level are required to perform the cross-connect, ADM and other network switching functions. Two of the primary functions are optical add-drop multiplexers (OADM) and wavelength-selective cross-connects (WSXC).
In order to perform wavelength routing functions optically today, the light stream must first be de-multiplexed or filtered into its many individual wavelengths, each on an individual optical fiber. Then each individual wavelength must be directed toward its target fiber using a large array of optical switches commonly called an optical cross-connect (OXC). Finally, all of the wavelengths must be re-multiplexed before continuing on through the destination fiber. This compound process is complex, very expensive, decreases system reliability and complicates system management. The OXC in particular is a technical challenge. A typical 40-80-channel DWDM system will require thousands of switches to fully cross-connect all the wavelengths. Opto-mechanical switches, which offer acceptable optical specifications, are too big, expensive and unreliable for widespread deployment. New integrated solid-state technologies based on new materials are being researched, but are still far from commercial application.
Consequently, the industry is aggressively searching for an all-optical wavelength routing solution that enables cost-effective and reliable implementation of high-wavelength-count systems.
Embodiments of the invention provide a microstructure for steering light that provides enhanced flexibility. The microstructure may be configured to function as an optical switch for directing an optical signal from a single input port to one of at least three output ports. Such configurations may be adapted for use in a wavelength router. Alternatively, the flexibility of the microstructure may be used to achieve improved alignment so that the light-steering efficiency is improved.
In one embodiment, a pivot member is connected with a structural film and supports a base that includes a reflective coating. The reflective coating may comprise gold. The pivot member may be a post pivot. At least three noncollinear fixed rotational actuators are connected with the structural film, each being configured to deflect the base towards the structural film upon activation. A movable hard stop connected with the structural film may additionally be included in some embodiments. In that case, the base assumes one of a plurality of tilt positions according to which of the fixed rotational actuators is activated and according to a position of the movable hard stop. The movable hard stop may be linearly actuated. In certain embodiments, it comprises a plurality of discrete levels, each of which contacts the base in one of the tilt positions.
Some embodiments include a plurality of noncollinear such movable hard stops. In one embodiment, the number of movable hard stops is equal to the number of fixed rotational actuators. In another embodiment, a subset of the movable hard stops are configured to move collinearly, such as by being connected with each other.
Further embodiments provide a method for steering light from an input port to one of a plurality of output ports. A micromirror assembly is tilted among at least three tilt positions that correspond to three of the output ports. The arrangement is two-dimensional in the following sense. For any two tilt positions, a tilt axis may be defined as the axis along which the micromirror assembly is tilted to move from one of the two tilt positions to the other. At least one additional tilt position is provided that cannot be reached from either of those two tilt positions by tilting the micromirror assembly along the tilt axis. Instead, such an additional tilt position requires that there at least be a tilt component in a direction orthogonal to the tilt axis. Light is then reflected off the micromirror assembly from the input port to one of the output ports.